Chinese Alcohol Distillation Technology

Da Qu had been used for spirit production for nearly 1000 years,little change in process modification has been made before the founding of the People's Republic of China although some scientists had engaged in studing of microbiology in Da Qu during the period of 1930's-1940's. Since 1950's, a series of researches on microbiology and process modification in Da Qu preparation has carried out. The achievements worth mentioning are listed below:

Isolation of useful microorganisms aimed to increase the saccharifying and fermenting ability ofDa Qu and raise the yield of ethanoal production.

Traditional fermentation processes for spirit were practiced for hundreds years but they were not well understood.These processes have widely been studied in modern times. In 1950's and 1960's, "the Typical Operation Method in Yantai Distillery" which was based on the techniques and experience in ethanol industry was comprehensively summed up. The key techniques included production of saccharifying agent (called "Bran QU" which was a artificial culture of mold by using wheat bran as the raw material, and pure culture of yeast used for fermentation. And "the Typical Operation Method in Yantai Distillery" also combined with the traditional production process of spirits. So, this operation method become the standard operation process for producing common spirits whose output is the largest in all Chinese spirits.
The production process for Luzhou- flavour Type Spirit which has been intensively studied by many factories and research institutes. The main achievements are list below:

(1) Temperature patterns during fermentation and its control model People have concluded: the initial temperature of fermenting grains should be appropriate, rising of temperature should be slow at the first stage and maintained constant at the second stage and decreased slowly at the final stage.

(2) Refermentation operation:- Refermentation operation includes:

Refermentation of the distilled spent grains aimed at increasing yield of ethanol and recovering of flavour substances.

Refermentation of the low quality spirits aimed at obtaining high quality spirits.

The fermentation of Luzhou-flavor spirits uses the fermenting pits clay as the support to preserve and multiply the microorganisms that producea lots of flavour substances. Under natural conditions, it will take a long time to build up a efficient pit to produce high quality spirit. So called man-made fermenting pits are developed by "artificial" cultivation of useful microorganisms in pit clay. This technique shortened the period of building up a efficient fermenting pit.

Distillation techniques for high quality Chinese spirits aremainly based on solid state distillation. It was recognized that thedistilling operation is very important to determine the quality and quantity of spirits produced. Some new distillation techniques are proposed and practiced in distilleries, including:

slowly distilling and carefully controlling the temperature.

seperately collecting spirits according to alcohol content and flavor characters.

In abroad, the alcohol content of distilled spirits is relatively low, being about 40%, but in China, due to the history reason and itself characteristic, the alcohol content of most of spirits is about 60%, usually about 55%, for the flavor and taste of the highalcohol spirit are fine than that of low alcohol content spirits dueto low solubility of some esters exsiting in Chinese spirits. As the increase of living conditions, comsumers are prefer low alcoholic drinks.Because it was considered that high alcohol spirits are harmful tohealth,So it is necessary to develop low alcohol content spirit.
There are two kinds of processes for production of low alcohol content spirit currently used in China. The most successful one is to chose the fine spirit as main ingredient and add water into it to adjust to appropriate concentration of alcohol, then the low alcohol spirits are blend with flavor-enhancing constitute. After being stored and filtered, the products can be consumed.Another one is to blend and add flavor- enhancing constitute firstly, then add water to low down the alcohol content of spirit. Because of the low alcohol content of the spirit,it is difficult for some flavoring substances to be dissolved in it. Some sediments(mainly consisted of esters) appeared after adding water to it. It is necessary to remove sediments and to purifying the water used.
Now a lots of famous Chinese spirits are produced in the form oflow alcohol content. The alcohol content are about 40 % (v/v). They arebecoming more and more popular in China.

The flavor substances exsited in various types of Chinese spiritshave been studied in recent decades. Besides ethanol, there are hundreds of chemical ingredients which can be divided into four kinds: alcohols, esters,organic acids, aldehydes and ketone. The character flavour substances in various types of Chinesespirits have been extensively investigated. It was identified that the character flavour substance in Fen- flavor spirits is mainly ethyl acetate, that of Luzhou flavor spirits is mainly ethyl hexanoate and ethyl butyrate; and that of Rice-flavor spirits is ethyl lactate plus ethyl acetate.
Much work still remaine to be studied in this field.

Traditionally, blending was undertook by experienced brewmaster according to their sensory evaluation, resulting fluctuating quality of spirits. Chemical and instrumental analysis of compositions in spirits combined with pilot test now is popular practice in most large scale distilleries, and blending technique based on computer is undergoing in some distilleries.

Traditionally produced spirit were stored and aged in ceramic vats,It took a long time for the spirits to be matured before being put into markets. Shortening the storage time by physical means and big- tank storing and aging techniques have been adopted in some distilleries.

From ancient times to 1940's, all work in distilleries were carried out by manual operation which were labour consuming. Since the founding of the People's Republic of China,many works have been done by means of mechanization operation.For example, Da Qu is shaped to block by machine instead of treading by foot. The traditional "top pot" for cooling the condensate when carrying out distillation was replaced by coil cooler, resulting easily controlling of temperature. Transportation of raw materials or fermented grains by belt or chain conveyer replaced the man power, reducing workers' labor intensity. Combination of three or four distillers made it possible that the solid state distillation be performed in continuos manner.